Necessary and sufficient optimality conditions for fractional multi-objective problems

Using a special scalarization, we give necessary optimality conditions for fractional multiobjective optimization problems. Under a generalized invexity, sufficient optimality conditions are also given. All over the article, the data are assumed to be continuous but not necessarily Lipschitz.     

半度量空间的刻画

We use the notions of weak base g-functions and pair networks to give some new characterizations of semi-metric spaces.     

Preparation and Characterization of Styrene/Butyl Acrylate Emulsifier-Free Latex with 2-Acrylamido-2-Methyl Propane Sulfonic Acid as a Reactive Emulsifier

A kind of emulsifier-free latex (FL) was successfully synthesized from styrene (St) and butyl acrylate (BA) with 2-acrylamido-2-methyl propane sulfonic acid (AMPS) as a reactive emulsifier. The particle size of latex particles, stability against electrolytes, minimum film forming temperature (MFT) and water contact angle (CA) were evaluated and compared with a conventional latex (CL). Test results show that FL has larger particle size, better stability against electrolytes and lower MFT value compared with CL; higher AMPS content leads to smaller particle size and smaller water CA.     

Antibacterial and Antifungal Activities—Surface Active Properties Relation of Novel Dischiff Base Cationic Gemini Amphiphiles Bearing Homogeneous Hydrophobes

A novel series of cationic Gemini amphiphiles containing Dischiff base species were synthesized and their chemical structures were determined using different analytical tools. Their surface properties were determined using surface tension measurements. The adsorption and micellization thermodynamic parameters were calculated using Gibb's equations at 25°C. The surface parameters were also determined including critical micelle concentration, effectiveness, efficiency, maximum surface excess, minimum surface area, interfacial tension, and emulsification power. The synthesized cationic Gemini surfactants were evaluated as bactericides for gram negative and gram positive bacteria and also against sulfur reducing bacteria (SRB). The results of the cytotoxicity of the synthesized compounds against the targeted bacterial strains were promising and completely dependent on the surface activity of these compounds.     

Existence of global weak solutions for Navier‐Stokes‐Poisson equations with quantum effect and convergence to incompressible Navier‐Stokes equations

In this paper, we consider a three dimensional quantum Navier‐Stokes‐Poisson equations. Existence of global weak solutions is obtained, and convergence toward the classical solution of the incompressible Navier‐Stokes equation is rigorously proven for well prepared initial data. Furthermore, the associated convergence rates are also obtained. Copyright © 2014 John Wiley & Sons, Ltd.     

An unusual conformation of gabapentin (Gpn) in Pyr‐Gpn‐NH‐NH‐Pyr stabilized by weak interactions

The crystal structure of N‐[(1‐{2‐oxo‐2‐[2‐(pyrazin‐2‐ylcarbonyl)hydrazin‐1‐yl]ethyl}cyclohexyl)methyl]pyrazine‐2‐carboxamide monohydrate (Pyr‐Gpn‐NN‐NH‐Pyr·H₂O), C₁₉H₂₃N₇O₃·H₂O, reveals an unusual trans–gauche (tg⁻) conformation for the gabapentin (Gpn) residue around the C^γ—C^β (θ₁) and C^β—C^α (θ₂) bonds. The molecular conformation is stabilized by intramolecular N—H...N hydrogen bonds and weak C—H...O interactions. The packing of the molecules in the crystal lattice shows a network of strong N—H...O and O—H...O hydrogen bonds together with weak C—H...O and π–π inteactions.     

Linear Group 13 E≡E Triple Bonds in E2Li62+

The triply bonded heavier main-group compounds have a textbook trans-bent geometry, in contrast to a familiar linear form found for the lightest analogues. Strikingly, the unexpected linear group 13 E≡E triple bonds were herein found in the D_4h-symmetry E₂Li₆²⁺ clusters, and they possess a large barrier (>18.0 kcal/mol) towards the dissociation of Li⁺. The perfectly surrounded Li₄ motifs and two linear coordinated Li atoms strongly suppress the increasing nonbonded electron density of heavier E atoms, making two degenerate π bonds and one multi-center σ bond in linear heavier main-group triple bonds. The surrounding Li₆ motifs not only creates an effective electronic structure to form a linear E≡E triple bond, but the resulting electrostatic interactions account for the highly stable global E₂Li₆²⁺ clusters.     

GeH/π层间弱相互作用调控锗烯电子结构的机制

锗烯是继石墨烯、硅烯发现以来最重要的二维纳米材料之一, 以其优异的物理化学性质迅速得到人们的广泛关注. 然而, 锗烯具有的零带隙能带特点(狄拉克点)极大程度地限制了其在微电子纳米材料方面的应用. 本文采用范德华力修正的密度泛函计算方法, 研究了锗烯、锗烷、锗烯/锗烷的几何和电学性质. 研究发现, 锗烯和锗烷可以通过弱相互作用形成稳定的双层结构, 并在锗烯中打开一个85 meV的带隙. 电子结构分析表明, Ge-H/π 的存在破坏了锗烯子晶格的对称性, 从而在狄拉克点上打开一个带隙. 差分电荷密度图分析表明有部分电荷从H原子的s轨道转移至Ge的p_z轨道. 该电荷转移机制增强了锗烯与锗烷之间的相互作用力, 是形成锗烯/锗烷双层二维纳米结构的主要原因. 进一步研究还发现, 锗烷/锗烯/锗烷的三明治结构无法在锗烯中打开带隙. 这是由于两侧的锗烷对夹层的锗烯作用力等价, 无法破坏锗烯的子晶格对称性, 所以无法打开锗烯带隙. 最后, 所有计算结果都在高精度杂化密度泛函HSE06计算精度下得到进一步验证. 因此, 本文从理论上提出了一种切实可行的打开锗烯狄拉克点的方法, 为锗烯在场效应管和其他纳米材料中的应用提供了理论指导.     

类Liu系统在水声微弱信号检测中的应用研究

利用三阶混沌系统构造了一种新的微弱信号检测系统——类Liu系统, 对类Liu 系统进行了深度的理论分析. 类Liu系统中, 当输入待测信号幅值大于某临界值时, 系统可达到平衡点S₀, S₀中系统变量x平衡于摄动力信号, 系统变量y, z收敛于零态, 且S₀ 对应的Lyapunov指数小于零. 通过Matlab仿真、Multisim电路仿真以及实际电路证明了类Liu系统的周期态收敛性及广域检测性, 解决了传统Duffing系统进行微弱信号检测时周期态不收敛、只能进行窄域检测等问题, 同时谱级信噪比范围仍可达-46.57 dB. 类Liu系统采用了全新的设计理念, 具有较高的实用价值, 对未来海洋物联网中的水声通信有一定参考价值.